Display screen are the primary visual display interface to a computer. One problem with these visual display screens is that they are limited in size, thus presenting a challenge to user interface design, particularly when larger amounts of information is to be displayed. This problem is normally referred to as the “screen real estate problem”.
Well-known solutions to this problem include panning, zooming, scrolling or combinations thereof. While these solutions are suitable for a large number of visual display applications, these solutions become less effective where the visual information is spatially related, such as maps, newspapers and such like. In this type of information display, panning, zooming and/or scrolling is not as effective as much of the context of the panned, zoomed or scrolled display is hidden.
A recent solution to this problem is the application of “detail-in-context” presentation techniques. Detail-in-context is the magnification of a particular region of interest (the “focal region”) in a data presentation while preserving visibility of the surrounding information. This technique has applicability to the display of large surface area media, such as maps, on limited size computer screens including personal digital assistance (PDA's) and cell phones.
In the detail-in-context discourse, differentiation is often made between the terms “representation” and “presentation”. A representation is a formal system, or mapping, for specifying raw information or data that is stored in a computer or data processing system. For example, a digital map of a city is a representation of raw data including street names and the relative geographic location of streets and utilities. Such a representation may be displayed visually on a computer screen or printed on paper. On the other hand, a presentation is a spatial organization of a given representation that is appropriate for the task at hand. Thus, a presentation of a representation organizes such things as the point of view and the relative emphasis of different parts or regions of the representation. For example, a digital map of a city may be presented with a region magnified to reveal street names.
In general, a detail-in-context presentation may be considered as a distorted view (or distortion) of a portion of the original representation where the distortion is the result of the application of a “lens” like distortion function to the original representation. A detailed review of various detail-in-context presentation techniques such as Elastic Presensation Space (“EPS”) may be found in a publication by Marianne S. T. Carpendale, entitled “A Framework for Elastic Presentation Space” (Carpendale, Marianne S. T., A Framework for Elastic Presentation Space (Burnaby, British Columbia: Simon Fraser University, 1999)), and incorporated herein by reference.
Development of increasingly powerful computing devices has lead to new possibilities for applications of detail-in-context viewing.
One shortcoming of the prior art detail-in-context presentation methods is their inability to effectively invert distortions in a detail-in-context presentation back to an original or undistorted presentation of the representation. The ability to perform such an inversion or inverse mapping would be of great value in extending the capabilities of detail-in-context presentations to applications such as image editing. For example, the editing of a focal region in a representation may be facilitated more easily in a distorted presentation rather than in an undistorted presentation.
The ability to perform an inverse mapping is also necessary for applications involving the subsequent distortion of a previously distorted presentation. In other words, inversion would allow a presentation system user to accurately position or reposition one or more distortion producing “lenses” within a given presentation that has already been distorted. Hence, the distorted presentation ultimately viewed by the user may be the end result of a series of distortion steps wherein the individual distortion steps are not known or are difficult to invert. In fact, the need for inversion arises whenever it is necessary to position a lens based on observed coordinates in the distorted presentation. This is so because the lens may be directly generated only from coordinate information in the undistorted presentation. As such, an inversion is necessary to produce the source coordinates for generating the lens.
Moreover, inversion provides a means to calculate real distances in an undistorted presentation based on locations within one or more lenses in a corresponding distorted presentation. For example, if a user wants to know the distance in the undistorted presentation between the focal points of two separate lenses in a corresponding distorted presentation of a map, such as the distance between a current location and a destination location, this distance can be computed via inversions of the focal points of these lenses.
Several systems are known which provide techniques for converting distorted or warped three-dimensional (3D) images into corrected, undistorted, or dewarped two-dimensional (2D) images. In U.S. Pat. No. 6,005,611, to Gullichsen, et al., a system is disclosed wherein a distorted image captured by a wide-angle or fisheye lens is corrected through the use of a specially generated polynomial transform function that maps points from the distorted image into rectangular points. A more complex transform function is described in U.S. Pat. No. 5,185,667, to Zimmerman. In U.S. Pat. No. 5,329,310, to Liljegern, et al., a similar objective is achieved in the context of motion picture images through the use of multiple lens (i.e. camera and projector) transfer functions. The result being the ability to project an image, taken from a particular point of view, onto a screen, especially a curved wide angle screen, from a different point of view, to be viewed from the original point of view, without distortion. In U.S. Pat. No. 5,175,808, to Sayre, a method and apparatus for non-affine image warping is disclosed that uses displacement tables to represent the movement of each pixel from an original location in a source image to a new location in a warped destination image. Through these displacement tables and a resampling method, the need for inversion of the underlying transform equation that specify the distortion or warp is eliminated. Finally, in U.S. Pat. No. 4,985,849, to Hideaki, look-up tables are used in combination with the forward evaluation of the transform equation in order to avoid the step of transform equation inversion. However, none of these systems disclose a method and system for inverting distortions in a manner that is optimized for detail-in-context presentations.
In U.S. patent application Ser. No. 09/932,088, assigned to the applicant of the present invention, a method and system for inverting distortions for detail-in-context presentations is disclosed. However, the method disclosed does not adequately invert distortions That include extreme “folding” as described by Carpendale. Folding occurs in a detail-in-context presentation, for example, when the applied distortion causes an undistorted surface of the presentation to be hidden by a portion of the distorted surface when viewed by a user on a computer display screen.
A need therefore exists for the effective inversion of distortions, including folds, in detail-in-context presentations in detail-in-context presentation systems. Consequently, it is an object of the present invention to obviate or mitigate at least some of the above mentioned disadvantages.